👉 Caltrops are a fictional term used in the science fiction novel "The Martian Chronicles" by David Brin. The term refers to a type of rock that is formed when Mars' atmosphere becomes depleted and the planet's surface begins to crumble under the force of gravity. In the novel, Caltrops are described as being made up of small crystals or particles that have been created through the process of hydrothermal venting in a volcano. These rocks are highly toxic and can cause severe harm